Process for sulfiding catalyst in a column

ABSTRACT

A process for the sulfiding of a hydrodesulfurization catalyst for example in a distillation column reactor. The catalyst in the distillation column reactor is first dried using nitrogen and the reactor is filled with a sulfiding solvent and circulation begun. The reactor is heated to a temperature above the decomposition temperature of the sulfiding agent to be used and the sulfiding agent charged to the reactor. When sulfiding agent breakthrough is noted in the overheads the temperature is raised and held until sulfiding is complete.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a process for thesulfiding of a hydrodesulfurization catalyst in a distillation columnreactor. More particularly the invention relates to a process wherein asulfiding agent such as H₂S and a solvent are concurrently fed through adistillation column containing a hydrodesulfurization catalyst thatcontain hydrogenation metals in their oxide state.

[0003] 2. Related Information

[0004] Hydrodesulfurization is a process for removing organic sulfurcompounds from petroleum streams by converting the sulfur in the organicsulfur compounds to H₂S. The process necessarily incorporateshydrogenation and thus requires hydrogenation catalysts. Water is also aproduct of the sulfiding reaction and must be removed.

[0005] Catalysts which are useful for the hydrodesulfurization reactioninclude Group VIII metals such as cobalt, nickel, palladium, alone or incombination with other metals such as molybdenum or tungsten on asuitable support which may be alumina, silica-alumina, titania-zirconiaor the like. Normally the metals are provided as the oxides of themetals supported on extrudates or spheres and as such are not generallyuseful as distillation structures.

[0006] The catalyst may also contain components from Group V, and VIBmetals of the Periodic Table or mixtures thereof. The Group VIII metalprovides increased overall average activity. Catalysts containing aGroup VIB metal such as molybdenum and a Group VIII such as cobalt ornickel are preferred. Catalysts suitable for the hydrodesulfurizationreaction include cobalt-molybdenum, nickel-molybdenum andnickel-tungsten. The metals are generally present as oxides supported ona base such as alumina, silicaalumina or the like. If the active form ofthe metal, the sulfide, is exposed to air, it begins to oxidize whichcan create a hazard.

[0007] The catalyst beds as used in the present invention may bedescribed as fixed, meaning positioned in a fixed area of the column andinclude expanded beds and ebulating beds of catalyst. The catalysts inthe beds may all be the same or different so long as they carry out thefunction of hydrogenation as described. Catalysts prepared asdistillation structures are particularly useful in the presentinvention.

SUMMARY OF THE INVENTION

[0008] The metals contained in the hydrogenation catalysts must beconverted from the stable oxide form to the reduced sulfide form to beuseful for hydrodesulfurization. Because of the unique combinationreactor distillation column, a unique method of reducing the oxide tothe sulfide is needed. Briefly the invention is a process for sulfidinga hydrodesulfurization catalyst which comprises:

[0009] (a) drying the catalyst with nitrogen;

[0010] (b) supplying the distillation column reactor with a sulfidingsolvent, preferably containing organic sulfur;

[0011] (c) establishing hydrocarbon feed and hydrogen flow rates;

[0012] (d) optionally, recycling of sulfiding solvent to supply tank;

[0013] (e) heating the distillation column reactor to a temperatureabove the decomposition temperature of the sulfiding agent, preferablyin the range of 300-500° F.;

[0014] (f) introducing a sulfiding agent;

[0015] (g) observing breakthrough of the sulfiding agent in the overheadand increasing the temperature to a target temperature, preferably inthe range of 500-700° F., upon said breakthrough; and

[0016] (h) holding the target temperature for a period of time.

[0017] After the treatment the unit may be switched to normal feed forhydrodesulfurization. The concurrent flow of the sulfiding agent andsolvent is preferably upflow but could also be downflow. Hydrogen mayalso be fed either concurrently or countercurrently. Water by-product isremoved overhead when operated in a distillation mode.

[0018] The process is preferably operated in a reactive distillationmode, although it can be operated without boiling or distillation. Theterm “reactive distillation” is used to describe the concurrent reactionand fractionation in a column. For the purposes of the presentinvention, the term “catalytic distillation” includes reactivedistillation and any other process of concurrent reaction and fractionaldistillation in a column regardless of the designation applied thereto.

BRIEF DESCRIPTION OF THE DRAWING

[0019]FIG. 1 is a flow diagram in schematic form of one embodiment ofthe invention.

[0020]FIG. 2 is a flow diagram in schematic form of a second embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The catalysts contain components from Group V, VIB, VIII metalsof the Periodic Table or mixtures thereof. The Group VIII metal providesincreased overall average activity. Catalysts containing a Group VIBmetal such as molybdenum and a Group VIII such as cobalt or nickel arepreferred. Catalysts suitable for the hydrodesulfurization reactioninclude cobalt-molybdenum, nickel-molybdenum and nickel-tungsten. Themetals are generally present in the catalyst precursor as oxidessupported on a neutral base such as alumina, silica-alumina or the like.

[0022] Referring now to FIG. 1 there is shown a flow diagram inschematic form of one embodiment of the invention. A distillation columnreactor 10 is provided having a bed 12 of hydrodesulfurization catalystin a distillation reaction zone. In this embodiment the catalyst isprepared as a distillation structure.

[0023] Feed to the distillation column reactor 10 is via flow line 101through feed heater 50. A sulfiding solvent is fed via flow line 103 andsulfiding agent via flow line 104. The sulfiding solvent and sulfidingagent are combined in flow line 108 and fed along with bottoms in flowline 105 to reboiler via flow line 106. Hydrogen is fed to the reboilervia flow line 102. All of the material is heated in reboiler 40 and fedto distillation column reactor 10 via flow line 107. Overheads are takenvia flow line 109 and passed through partial condenser 20 with thecondensible material collected and separated from the gaseous materialin separator/receiver 30. The vapors are vented via flow line 110. Thecondensed material is removed and may be removed via flow line 111 orreturned to the distillation column reactor 10 as reflux via flow line112.

[0024] In a preferred embodiment the solvent is a heavy hydrocarbonstream which has very low olefin (less than 1 wt %)and organic nitrogencontent (less than 100 wppm). A highly hydrotreated jet fuel, dieselfuel, or kerosene would be suitable. The pressure in the column is setat or above the vapor pressure of the solvent at 450° F. and the solventis heated to between 400 and 450° F. in the reboiler 40. At this pointliquid from the bottoms (from line 108) is pumped to the top of thecolumn via flow line 107 a. If the solvent is boiling and overheads arebeing taken then the reflux in flow line 112 may be substituted for thepumped liquid in flow line 107 a. In either case it is important thatthere is liquid flowing over the catalyst during the sulfiding step. Theliquid which flows over the catalyst helps to heat up the catalyst tothe desired sulfiding temperature and absorb the heat released by thesulfiding process. In this way temperature excursions during sulfidingare avoided. In this particular embodiment the column is not liquidfilled but operated with a continuous vapor phase like a typicaldistillation column. Gas and liquid are flowing counter currently in thecolumn.

[0025] The sulfiding agent and hydrogen are injected into the reboilerwhere the reaction takes place to generate H₂S. The flow rate ofhydrogen and sulfiding agent are set such that a molar ratio H₂S:H₂ isbetween 1:25 and 1:5 is obtained following the reaction. Typically aratio of 1:9 is preferred.

[0026] The hydrogen and H₂S, along with vaporized hydrocarbons passesupward through the catalyst bed where sulfiding takes place. The ventgas is monitored to measure the H₂S concentration. Once the H₂S ismeasured at its full concentration based upon that being produced in thereboiler, the temperature is the column is raised to 600° .F or higheras required. This is achieved by increasing the reboiler duty and/orraising the operating pressure. Once 600° F. is reached throughout theentire column the vent gas is once again monitored for H₂S. Once thefinal breakthrough is confirmed at 600° F. the column may be cooled downto await startup, or the feed can be brought in and the unit can bestarted up directly.

[0027] Referring now to FIG. 2 a second embodiment is shown for use whenthe reboiler 40 does not have sufficient capacity to supply the heatnecessary. The hydrogen is fed through the reboiler 40 as in the firstembodiment. However the sulfiding solvent in flow line 103 and sulfidingagent in flow line 104 are fed through the feed heater 50. After heatingthe solvent and agent may be fed at the top of the column via line 113or near the bottom via line 114.

[0028] A common sulfiding agent is H₂S because it is readily availablein most refineries. Preferred sulfiding agents include tertiary nonylpoly sulfide (TNPS) and dimethyl disulfide, because they are availableas liquids and their use facilitates exact control of the amount ofsulfur in the column at one time. Another useful sulfiding agent iscarbon disulfide. A suitable sulfiding agent is any organic or inorganicsulfur compound that will decompose under the conditions of treatment toconvert the catalyst to a sulfide. The solvent can be chosen from anystream that will boil at the pressure in the reactor, preferably ahighly hydrotreated jet fuel, naphtha, kerosene or diesel. The presenceof organic sulfur compounds in the solvent is believed to provide anadditional source of sulfiding agent.

[0029] The target temperatures and times depend on the type of catalyst,especially the metals composition and support to obtain the optimumdegree of sulfiding for use of the catalyst in hydrodesulfurizationprocesses. Generally the catalyst manufacturer provides the optimumsulfiding conditions.

EXAMPLE

[0030] A load of Co/Mo desulfurization catalyst was sulfided using asynthetic jet fuel with the a 5 vol % boiling point of 317° F., a 50 vol% boiling point of 421° F. and a 95 vol % boiling point of 581° F. Theolefin content of the jet fuel was very low (bromine number <0.2) andthe nitrogen content was 1.07 mg/liter and the sulfur content was 235mg/liter. The low temperature sulfiding was completed at 450° F. and 65psig. The pressure was then raised to 220 psig for the 600° F.sulfiding. The final catalyst was then tested for the desulfurization ofgasoline where its usefulness was confirmed.

The invention claimed is:
 1. A process for the sulfiding of a hydrodesulfurization catalyst comprising the steps of: (a) contacting the hydrodesulfurization catalyst with a solvent heated to a first temperature above the above the decomposition temperature of a sulfiding agent and hydrogen; (b) introducing the sulfiding agent; (c) observing a sulfiding agent breakthrough and increasing temperature to a second temperature higher than said first temperature; and (d) holding said second temperature for a period of time.
 2. A process for the sulfiding of a hydrodesulfurization catalyst comprising the steps of: (a) drying the catalyst; (b) establishing solvent feed and hydrogen flow rates; (c) heating the solvent to a first temperature above the above the decomposition temperature of a sulfiding agent; (d) introducing the sulfiding agent; (e) observing a sulfiding agent breakthrough and increasing temperature to a second temperature higher than said first temperature; and (f) holding said second temperature for a period of time.
 3. The process according to claim 2 wherein said sulfiding agent comprises tertiary nonyl poly sulfide.
 4. The process according to claim 2 wherein said sulfiding agent comprises dimethyl disulfide.
 5. The process according to claim 2 wherein the sulfiding agent comprises H₂S.
 6. The process according to claim 2 wherein the column is filled with solvent prior to step (b).
 7. The process according to claim 2 wherein the solvent is moving upflow through said catalyst.
 8. The process according to claim 2 wherein the solvent is moving downflow through said catalyst.
 9. The process according to claim 2 wherein the sulfiding agent and sulfiding agent are co-currently fed.
 10. The process according to claim 2 wherein said catalyst comprises components from Group V, VIB, VIII metals of the Periodic Table or mixtures thereof.
 11. The process according to claim 10 wherein said catalyst comprises an oxide of said components from Group V, VIB, VIII metals of the Periodic Table or mixtures thereof.
 12. The process according to claim 2 wherein the sulfiding is carried out at a pressure that it is above the vapor pressure of the solvent at the first temperature.
 13. The process according to claim 2 wherein the first temperature is in the range between 300 and 500° F.
 14. The process according to claim 2 wherein the second temperature is in the range between 500-700° F.
 15. A process for the sulfiding of a hydrodesulfurization catalyst in a distillation column reactor comprising the steps of: (a) drying the catalyst with an inert gas; (b) filling the distillation column reactor with a sulfiding solvent containing sulfur; (c) establishing hydrocarbon feed and hydrogen flow rates; (d) begin recycling of sulfiding solvent; (e) heating the distillation column reactor to a temperature above the decomposition temperature of the sulfiding agent; (f) introducing a sulfiding agent; (g) observing the water by-product azeotrope overhead and collecting the water; (h) observing said sulfiding agent breakthrough in the overhead; (i) increasing temperature to a second temperature; (j) holding said second temperature for a period of time; and (k) switching unit to normal feed.
 16. The process according to claim 15 wherein said sulfiding agent comprises H₂S.
 17. The process according to claim 15 wherein said solvent comprises a sulfur containing naphtha stream.
 18. The process according to claim 17 wherein the sulfiding solvent and sulfiding agent are fed downflow.
 19. The process according to claim 15 wherein the sulfiding solvent and sulfiding agent are fed downflow.
 20. The process according to claim 15 wherein heating of step (c) is obtained by heating a bottom portion in the column.
 21. The process according to claim 20 wherein the reboiler is operated at a temperature sufficient to dissociate the sulfiding agent into its constituent elements.
 22. The process according to claim 16 wherein said catalyst comprises components from Group V, VIB, VIII metals of the Periodic Table or mixtures thereof.
 23. The process according to claim 22 wherein said catalyst comprises an oxide of said components from Group V, VIB, VIII metals of the Periodic Table or mixtures thereof. 